Circuit arrangement and method for generating a drive signal for a transistor

ABSTRACT

Disclosed is a circuit arrangement for generating a drive signal for a transistor. In one embodiment, the circuit arrangement includes a control circuit that receives a switching signal, a driver circuit that outputs a drive signal, and at least one transmission channel. The control circuit transmits, depending on the switching signal for each switching operation of the transistor, switching information and switching parameter information via the transmission channel to the driver circuit. The driver circuit generates the drive signal depending on the switching information and depending on the switching parameter information.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.13/603,063, filed Sep. 4, 2012, which issued as U.S. Pat. No. 8,866,513,and is a Divisional of U.S. application Ser. No. 12/642,486, filed Dec.18, 2009, which issued as U.S. Pat. No. 8,258,820, and claims priorityto German Application No. DE 10 2008 055 051.5, filed on Dec. 19, 2008,the entire content of each of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a circuit arrangement and a method forgenerating a drive signal for a transistor, in one embodiment a MOStransistor.

BACKGROUND

MOS transistors, such as IGBTs or MOSFETs, for example, can be used aselectronic switches for switching electrical loads. During switchingoperations, that is to say during switching on and switching off of thetransistor, voltage and current changes occur at the load, in currentsupply lines to the transistor and the load, in a connecting linebetween the transistor and the load, and also in the transistor itself.In this case, the speed or gradient with which these voltage and currentchanges occur is dependent on the switching speed of the transistor,that is to say dependent on how rapidly the transistor switches on oroff.

The voltage and current changes which occur during the switching of atransistor can lead to electromagnetic interference pulses. Theamplitude of the interference pulses is dependent firstly on theswitching speed of the transistor and secondly on the interconnection ofthe transistor with the load, and here in one embodiment on the type andlength of the lines. There is a need to reduce the interference pulseswhich occur during the switching of a transistor.

For these and other reasons, there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

Various embodiments are explained below with reference to figures. Thefigures serve for elucidating the basic principle, and so only the partsor component zones required for understanding this basic principle areillustrated. In the figures, unless indicated otherwise, identicalreference symbols designate identical parts with the same meaning

FIG. 1 illustrates one embodiment of a circuit arrangement forgenerating a drive signal for a transistor, the arrangement including acontrol circuit, a transmission channel and a driver circuit.

FIG. 2 illustrates an operating principle of one embodiment of thecircuit arrangement on the basis of signal timing diagrams.

FIG. 3 illustrates the operating principle of a further embodiment ofthe circuit arrangement on the basis of signal timing diagrams.

FIG. 4 illustrates one embodiment of a transmission channel.

FIG. 5 illustrates another second embodiment of a transmission channel.

FIG. 6 illustrates an operating principle of a further embodiment of acircuit arrangement on the basis of signal timing diagrams.

FIG. 7 illustrates, on the basis of signal timing diagrams, an operatingprinciple of an embodiment of a circuit arrangement in the case of afault.

FIG. 8 illustrate one embodiment of information transmission from thecontrol circuit to the driver circuit via the transmission channel.

FIG. 9 illustrates another embodiment of information transmission.

FIG. 10 illustrates one embodiment of a transmission channel for theinformation transmission in accordance with FIG. 9.

FIG. 11 illustrates another embodiment of information transmission fromthe control circuit to the driver circuit.

FIG. 12 illustrates another embodiment of information transmission fromthe control circuit to the driver circuit.

FIG. 13 illustrates another embodiment of a transmission channel for theinformation transmission in accordance with FIG. 12.

FIG. 14 illustrates one embodiment of the control circuit on the basisof a block diagram.

FIG. 15 illustrates one embodiment of the driver circuit on the basis ofa block diagram.

FIG. 16 illustrates one embodiment of a current source circuit of thedriver circuit.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which isillustrated by way of illustration specific embodiments in which theinvention may be practiced. In this regard, directional terminology,such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc.,is used with reference to the orientation of the Figure(s) beingdescribed. Because components of embodiments can be positioned in anumber of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

It is to be understood that the features of the various embodimentsdescribed herein may be combined with each other, unless specificallynoted otherwise.

One embodiment provides a circuit arrangement for generating a drivesignal for a transistor. The circuit arrangement includes: a controlcircuit having an input for receiving a switching signal and having atleast one output; a driver circuit having at least one input and havingan output for providing the drive signal; at least one transmissionchannel, connected between the at least one output of the controlcircuit and the at least one input of the driver circuit. The controlcircuit of this circuit arrangement is configured to transmit, dependingon the switching signal for each switching operation of the transistor,switching information and switching parameter information via thetransmission channel to the driver circuit; and the driver circuit isconfigured to generate the drive signal depending on the switchinginformation and depending on the switching parameter information.

One embodiment provides a method for generating a drive signal for atransistor. The method includes, for each switching operation of thetransistor: providing switching information and switching parameterinformation; generating a first signal level of the drive signal afterproviding the switching information, and generating a second signallevel of the drive signal, the second signal level being dependent onthe switching parameter information, after providing the switchingparameter information.

FIG. 1 illustrates, on the basis of a block diagram, one embodiment of acircuit arrangement for generating a drive signal S3 for a transistor M.This circuit arrangement includes a control circuit 1, a driver circuit3, and also a transmission channel 2 arranged between the controlcircuit 1 and the driver circuit 3. The control circuit 1 has an input11 for receiving a switching signal S, and at least one output 12coupled to a transmitter-side end of the transmission channel 2. Thedriver circuit 3 has at least one input 31 coupled to a receiver-sideend of the transmission channel 2, and an output 32 for providing adrive signal S3 for the transistor M.

In order to afford a better understanding, a transistor M is likewiseillustrated in FIG. 1. In the example illustrated, the transistor is aMOS transistor, specifically an n-channel MOSFET. It should be pointedout that the use of an n-channel MOSFET should be understood merely asan example. The circuit arrangement illustrated is suitable for drivingany MOS transistors, that is to say also for driving IGBTs, or also fordriving bipolar transistors.

The transistor M driven by the circuit arrangement serves for examplefor switching a load Z connected in series with a load path of thetransistor M between terminals for a positive supply potential V+ and anegative supply potential or reference potential GND. The drive signalS3 is fed to a control terminal of the transistor M. In the case of theMOSFET illustrated in the example, its drain-source path D-S forms itsload path, and its gate terminal G forms the control terminal.

In the case of this circuit arrangement, the transmission channel 2serves for transmitting control information from the control circuit 1to the driver circuit 3. The transmission channel 2 can have a potentialbarrier, which will be explained below. Such a potential barrier isexpedient when the switching signal S fed to the control circuit 1 andthe drive signal S3 generated by the driver circuit 3 are referred todifferent reference potentials. This is the case for example when thetransistor M to be driven by the circuit arrangement is a MOS transistorconnected up as a high-side switch. As is known, a MOS transistor is avoltage-controlled component and turns on or turns off depending on avoltage between its gate terminal G and its source terminal. Thereference potential to which a drive signal S3 fed to the transistor isreferred, in the case of such a high-side transistor, is the sourcepotential thereof. The source potential varies depending on theswitching state of the transistor and can lie in the range of the uppersupply potential V+ when the transistor is turned on, and in the rangeof the negative supply potential or reference potential GND when thetransistor is turned off. By contrast, the switching signal S fed to thecontrol circuit 1 can be referred to a constant potential, such asreference potential GND, for example.

The switching signal S determines the desired switching state of thetransistor M, that is to say contains information about whether thetransistor M is to be driven in the on state or whether the transistor Mis to be driven in the off-state. The switching signal S may contain, inone embodiment, information about the instants at which the transistoris intended to be driven in the on-state or driven in the off-state. Theswitching signal S can be any signal suitable for supplying suchswitch-on information and switch-off information to the control circuit1. Referring to FIG. 2, the switching signal S is a two-valued signal,for example, which can assume a switch-on level and a switch-off level,where the transistor M is respectively to be switched on when theswitching signal S assumes a switch-on level, and is intended to beswitched off when the switching signal S assumes a switch-off level. Itshould be assumed for the further explanation that the switch-on levelof the switching signal S is a high level and the switch-off level ofthe switching signal S is a low level. These signal levels can also becorrespondingly interchanged. In the case of such a two-valued switchingsignal, the switching information for the transistor M is contained inlevel changes of this signal, where the transistor M is intended to beswitched on when a level change of the switching signal S from theswitch-off level to the switch-on level is present, and where thetransistor M is intended to be switched off when a level change from theswitch-on level to the switch-off level of the switching signal S ispresent. The use of a two-valued signal as switching signal S should beunderstood merely as an example. Any desired signal which is suitablefor transmitting switch-on and switch-off information for the transistorM is suitable.

The operating principle of the circuit arrangement illustrated in FIG. 1is explained in more detail below on the basis of timing diagramsillustrated in FIG. 2. FIG. 2 illustrates a timing diagram of theswitching signal S, a timing diagram of an information signal S1transmitted from the control circuit 1 to the driver circuit 3 via thechannel 2, of a drive signal S3 generated by the driver circuit 3, andalso the timing diagram of a drive voltage VGS of the transistor M thatresults from the drive signal S3. In the embodiment illustrated, thedrive signal S3 is a drive current that charges or discharges agate-source capacitance (not illustrated) of the transistor M.

In the embodiment illustrated in FIG. 2, a switch-on information in theform of a rising edge of the switching signal S is present at theinstant t1. The control circuit 1 is configured to detect this switch-oninformation contained in the switching signal S and to transmitcorresponding switching information In1 to the driver circuit 3 via thetransmission channel 2. For explanation purposes, it should be assumedthat the switching information representing a desired switch-on of thetransistor M is a positive signal pulse of the information signal S1.The control circuit 1 is additionally adapted to transmit, in additionto the switching information, switching parameter information In2 to thedriver circuit 3 via the transmission channel 2. Such switchingparameter information In2 may be transmitted by the control circuit 1for each switching operation of the transistor M.

The switching parameter information In2 contains information regardingthe course of the switching operation. The switching parameterinformation In2 can contain switching speed information, for example,which indicates the speed at which the transistor M is intended tochange its switching state, and which thus influences the gradient ofthe switching edges. The switching parameter information In2 may alsocontain information about what maximum amplitude a drive voltage of thetransistor is intended to achieve. The switching parameter informationIn2 can also contain delay information which defines a waiting timebetween the presence of the switching information and the beginning ofthe switching operation, for example.

As one of the switching parameters which are influenced by the switchingparameter information In2, the switching speed, in one embodiment, shallbe considered below. The switching speed of a MOS transistor is directlydependent on the amplitude of a drive current, that is to say, duringswitch-on, on the amplitude of a charging current flowing into thegate-source capacitance and, during switch-off, on a discharging currentflowing from the gate-source capacitance. In this case, the switchingparameter information In2 contains information about the desiredamplitude of the drive signal or drive current S3. The switchingparameter information In2 and the switching information In1 can betransmitted in any temporal sequence—defined and known to the drivercircuit—to the driver circuit.

As illustrated in FIG. 2, the switching parameter information In2 can betransmitted in one embodiment temporally after the switching informationIn1. In a departure from this, there is also the possibility oftransmitting the switching parameter information In2 temporally beforethe switching information In1 or transmitting the switching informationembedded into the switching parameter information In2, that is to saytemporally between two sequences of the switching parameter informationIn2. As will be explained below there is also the possibility oftransmitting the switching information In1 and the switching speedinformation In2 simultaneously via two parallel transmission channels tothe driver circuit 3.

The switching information In1 and the switching parameter informationIn2 form control information that is transmitted from the controlcircuit to the driver circuit 3. A time duration during which theseitems of control information In1, In2 are transmitted is designated byTc in the figures.

In FIG. 1, S1′ denotes an information signal available at thereceiver-side end of the transmission channel 2. In the case ofdisturbance-free transmission, this information signal S1′ available atthe receiver-side end corresponds to the transmitted information signalS1, and thus contains the switching information In1 and the switchingparameter information In2. Owing to signal propagation times in thetransmission channel 2, the information signal S1′ fed to the drivercircuit 3 can be temporally delayed relative to the information signalS1 transmitted by the control circuit. In order to simplify theillustration, such temporal delays during the transmission via thetransmission channel 2 and owing to signal propagation times within thecontrol circuit 1 and the driver circuit 3 are not taken into account inthe figures.

The driver circuit 3 is designed to generate the drive signal S3 in amanner dependent on the switching information In1 and in a mannerdependent on the switching parameter information In2. In the exampleillustrated, wherein the drive signal S3 is a charging current ordischarging current for the gate-source capacitance of the transistor M,the switching information In1 determines the sign of the drive signal S3and the switching parameter information In2 determines the temporalbehavior of the drive signal, and here in one embodiment the amplitudethereof. The switching parameter information In2 can be transmitted inthe form of a digital data word, which is illustrated schematically inFIG. 2.

In FIG. 2, t2 denotes an instant at which the switching parameterinformation In2 has been completely transmitted to the driver circuit 3.In this example, the driver circuit 3 is designed to maintain theprevious level of the drive signal S3 until this instant t2 and to setthe signal level of the drive signal S3 in accordance with the switchingparameter information In2 at the instant t2 or after the instant t2. Thesignal level represented by the switching parameter information In2 forthe switch-on operation is designated by L1 in FIG. 2. In the exampleillustrated, starting from the instant t2, the drive signal S3 has apositive sign, that is to say that a charging current flows onto thegate-source capacitance of the transistor M, whereby the gate-sourcevoltage VGS thereof rises starting from the instant t2.

In FIG. 2, t5 denotes an instant at which the threshold voltage Vth ofthe transistor M has been reached, starting from which threshold voltagethe transistor M begins to conduct. Owing to the known Miller effect,the drive voltage VGS, despite a flowing charging current, remains atthe value of the threshold voltage Vth for a time duration and thenrises further up to a maximum value. The maximum value is substantiallydetermined by the properties of a current source (not illustrated) inthe driver circuit 3 which provides the drive current or chargingcurrent S2. It should also be noted in this context that the timingdiagram of the drive voltage VGS is merely illustrated schematically inFIG. 2.

In FIG. 2, t3 denotes an instant at which the switching signal S1 hasswitch-off information in the form of a falling edge of the switchingsignal. At this instant, switching information In1 is generated by thecontrol circuit 1 and transmitted to the driver circuit 3. In theexample illustrated, this switching information for a switch-off of thetransistor M is a negative signal pulse of the information signal S1.After this switching information In1, switching parameter informationIn2 is transmitted which defines the amplitude of the drive signal S3for the switch-off operation. This amplitude for the switch-offoperation can differ from the amplitude for the switch-on operation,that is to say that the switching parameter information for theswitch-off operation can differ from the switching parameter informationfor the switch-on operation. In the example illustrated, the controlinformation is transmitted at the instant t4. Starting from thisinstant, the driver circuit 3 sets the drive signal S3 to the valuedesired for the switch-off operation. In the example illustrated, thedrive signal S3 has a negative sign for the switch-off operation, thatis to say that a discharging current flows from the gate-sourcecapacitance, the amplitude of the current being determined by theswitching parameter information In2 transmitted after the instant t3.The drive voltage VGS of the transistor M decreases after the instant t4owing to the discharging current, then remains at the value of thethreshold voltage Vth for a time duration owing to the Miller effect,and subsequently decreases further down to zero.

In the embodiment explained with reference to FIG. 2, a switchingoperation of the transistor M begins only after the switching parameterinformation In2 has been transmitted, that is to say—in the exampleillustrated—only at the end of the time duration Tc during which theitems of control information are transmitted. In order to accelerate theswitching operations, in a further example, the driver circuit 3 isdesigned to set, immediately after the presence of switchinginformation, a first signal level of the drive signal S3, the sign ofwhich takes account of the respective switching information, and onlyafter reception of the switching parameter information In2 to set thelevel of the drive signal S3 to the amplitude represented by theswitching parameter information In2. Associated temporal signal profilesare illustrated in FIG. 3.

In FIG. 3, t11 denotes an instant at which the switching information In1is present in the driver circuit 3. Starting from this instant, thedriver circuit 3 sets a first signal level L2 of the drive signal S3.The sign of this signal level takes account of the respective switchinginformation. In the example illustrated, the drive signal S3 has apositive sign if the switching information is switch-on information, anda negative sign if the switching information is switch-off information.The second signal level L1 of the drive signal corresponds to the signallevel L1 already explained above with reference to FIG. 2. The firstsignal level L2 can be greater or less than the second signal level L1.One example provides for the first signal level L2 to correspond to amaximum signal level which the drive signal S3 can assume for therespective switching operation, that is to say the switch-on operationor the switch-off operation. In this example, the drive voltage VGS ofthe transistor M changes as early as from the instant t11 at which theswitching information is present. In the switch-on operation illustratedstarting from the instant t1, the drive voltage VGS rises starting fromthe instant t11. The gate-source capacitance is hereby precharged beforethe switching parameter information is present at the instant t2 and thedriver circuit 3 sets the signal level of the drive signal S3 to thesecond value as a result of the switching parameter information In2. The“precharging” of the gate-source capacitance has no direct effect on theswitching edges of a load current switched by the transistor M or thevoltages present across the transistor M or the load Z, as long as thegate-source voltage VGS does not reach the threshold value Vth duringthis time duration. The first signal level L2 and the time duration Tcduring which the control information is transmitted should therefore becoordinated with one another such that the threshold voltage Vth of thetransistor M is not reached before the switching parameter informationhas been transmitted to the driver circuit 3. In FIG. 3, t6 denotes aninstant at which the threshold voltage Vth or the Miller plateau hasbeen reached.

In the embodiment illustrated in FIG. 3, a turn-off operation of thetransistor M functions in a manner corresponding to the switch-onoperation. At an instant t31, the turn-off information is present in thedriver circuit 3. The driver circuit 3 thereupon sets a first signallevel L4 of the drive signal S3 for the turn-off operation before theswitching parameter information is present at an instant t4 and thedriver circuit 3 sets the signal level for the turn-off operation to asecond level value L3, which is represented by the switching parameterinformation In2 for the turn-off operation.

The transmission channel 2 between the control circuit 1 and the drivercircuit 3 can be any transmission channel suitable for signaltransmission. The transmission channel 2 can contain—as alreadymentioned briefly—a potential barrier, in one embodiment. One example ofa transmission channel 2 having such a potential barrier is illustratedin FIG. 4. In the example illustrated, the potential barrier of thetransmission channel 2 is a transformer 22 having a primary winding 221and a secondary winding 222, which is inductively coupled to the primarywinding. The transformer 22 can be, in one embodiment, a transformerwithout a transformer core (coreless transformer) or air-core coil-typetransformer. Such transformers can be part of an integrated circuit inwhich the control circuit 1 and the driver circuit 3 can be integrated.The transmission channel 2 additionally includes a modulator 21, intowhich the information signal S1 is fed from the control circuit 1 andwhich is connected to the primary winding 221. This modulator 21 isdesigned to convert the information signal S1 made available by thecontrol circuit 1 to a signal suitable for transmission via thetransformer 22. A demodulator 23 is correspondingly connected to thesecondary winding 222, the demodulator being designed to convert thesignals transmitted from the primary winding 221 to the secondarywinding 222 into the information signal S1′ fed to the driver circuit 3.

Transformers, in one embodiment coreless transformers, are able totransmit the items of control information In1, In2 at a speed requiredfor the switching operation. If the control information is intended forexample to be transmitted within a time duration of 100 ns and if thecontrol information includes 5 bits, for example, then a transmissionrate of 50 Mbauds is necessary, which can be ensured without anyproblems by using coreless transformers. A high transmission speed forthe control information is necessary in one embodiment when—as in theexample in accordance with FIG. 3—the switching operation of thetransistor M is already initiated before the switching parameterinformation In2 is actually present. In this case, as already mentioned,it should be ensured that the switching parameter information is presentin the driver circuit 3 before the transistor M actually reaches itsthreshold voltage Vth and begins to change its switching state.

Referring to FIG. 5, instead of a transformer, it is also possible toprovide an optocoupler 25 for potential isolation in the transmissionchannel 2. On the transmitter side, a modulator 24 is connected to theoptocoupler 25 and converts the information signal S1 into signalssuitable for transmission via the optocoupler 25. On the receiver side,a demodulator 26 is connected to the optocoupler 25 and is configured toconvert signals transmitted via the optocoupler 25 into the informationsignal S1′ fed to the driver circuit.

FIG. 6 illustrates a further example of a circuit arrangement on thebasis of temporal signal profiles. FIG. 6 illustrates the signalprofiles for a switch-on operation of the transistor M. The switch-offoperation functions correspondingly. In this example, the controlcircuit 1 is designed to refresh the switching information In1 firsttransmitted at the instant t1, that is to say to transmit it again atleast once at a later instant, provided that no new switchinginformation is present in the switching signal S in the meantime. InFIG. 6, Tr denotes the temporal separation between the firsttransmission of switching information In1 and a first renewedtransmission of the switching information In1. As is illustrated bydashed lines in FIG. 6, the switching information In1 can be transmittedat regular time intervals Trp, but can also be transmitted anew atirregular time intervals, as long as no new switching information ispresent in the switching signal S, that is to say as long as—in relationto the example illustrated—the signal level of the switching signal Sdoes not change.

The explanations given above hold true for the first transmission of theswitching information In1 at the instant t2 and the transmission of theswitching parameter information In2, and also the generation of thecontrol signal S3 from these items of control information transmittedduring the time duration Tc. The driver circuit 3 can therefore generatethe control signal S3 in accordance with the explanations concerningFIG. 2, which is illustrated as a solid line in FIG. 6, or in accordancewith the explanations concerning FIG. 3, which is illustrated by thesolid and dash-dotted line in FIG. 6.

One embodiment provides for the control circuit to change, and in oneembodiment increase the signal level of the drive signal S3 startingfrom an instant t7 at which the switching information In1 is transmittedanew for the first time. This is illustrated on the basis of a dottedline in FIG. 6. The driver circuit 3 can be configured in one embodimentto output the maximum signal level of the drive signal S3 for therespective switching operation starting from the instant t7. In thiscase, the temporal separation between the first transmission of theswitching information and the first repeated transmission of theswitching information should be large enough that, at the instant t7 atwhich the level of the drive signal changes, the switching operation issubstantially concluded, such that the change in the signal level of thedrive signal S3 no longer affects the switching speed or the gradient ofthe switching edges.

FIG. 7 elucidates an operating principle of a further embodiment of thedriver circuit 3 on the basis of temporal signal profiles. This drivercircuit is designed to drive the transistor M in the off state if norenewed transmission of the switching information is determined after awaiting time Tw has elapsed after reception of the first switchinginformation In1. In this case, a fault in the control circuit 1 or thetransmission channel 2 is assumed, with the result that the transistor Mis turned off for safety reasons. This is illustrated in FIG. 7 by thefact that after the waiting time Tw has elapsed, the drive signal S3changes to a switch-off level, that is to say to a level at which thetransistor M is driven in the off-state.

The items of control information transmitted from the control circuit 1to the driver circuit 3 via the channel 2 can be coded in a desiredmanner. Examples of possible transmission methods are explained below.Referring to FIG. 8, the items of control information can be transmittedas binary coded data via a single transmission channel, where positivesignal pulses of the information signal S1 represent a first value, forexample a logic “1”, and negative signal pulses represent a secondvalue, for example a logic “0”, of the binary data to be transmitted.

In order to increase the transmission reliability, referring to FIG. 9,the binary data to be transmitted can in one option be transmitted indifferentially coded fashion. In this case, there are two transmissionchannels present between the control circuit 1 and the driver circuit 3,via which respectively complementary signal pulses are transmitted. Inthis case, the driver circuit 3 can be designed to accept onlycomplementary pulses on the two channels as information pulses.Interference pulses which would have an effect as common-mode pulses onboth channels therefore cannot incorrectly lead to a change in theswitching state of the transistor M. In FIG. 9, S1 denotes theinformation signal and S11, S12 denote the first and second informationsignals transmitted by the two channels, one of which, S11, correspondsto the information signal S1 in the example.

One embodiment of a transmission channel for the transmission explainedwith reference to FIG. 9 is illustrated in FIG. 10. In the embodimentillustrated, this transmission channel includes two transformers 221,222 having respectively a primary winding 2211, 2221 and a secondarywinding 2212, 2222. On the transmitter side a modulator 211, 212 and onthe receiver side a demodulator 231, 232 are connected to each of thetransformers 221, 222. The information signal S1 is fed to a first 211of the modulators directly and to a second 212 of the modulators in amanner inverted by using an inverter 27, such that respectivelycomplementary information signals are transmitted via the two channelsfor the transformers 221, 222. Two complementary information signalsS11′ and S12′ are correspondingly available at the output of thistransmission channel 2, the information signals being processed furtherby the driver circuit 3 in the manner explained.

The previously explained methods require modulators that are able totransmit both positive and negative signal pulses via the respectivechannel. In a further transmission method, illustrated in FIG. 11, thereare two transmission channels present, via which respectively oneinformation signal S11, S12 is transmitted. In this case, one of thesechannels serves for transmitting the bits with the logic 1 and the otherof the channels serves for transmitting the bits with logic 0 of thecontrol information. In this case, only positive signal pulses can betransmitted via each of these channels.

Referring to FIG. 12, a further embodiment provides for the switchinginformation In1 and switching parameter information In2 to betransmitted temporally in parallel via two parallel transmissionchannels. A first information signal S11 transmitted from the controlcircuit 1 to the driver circuit 3 contains the switching information inthis case, and a second information signal S12 transmitted from thecontrol circuit 1 to the driver circuit 3 contains the switchingparameter information In2 in this case.

FIG. 13 illustrates one embodiment of a transmission channel 2 for sucha transmission of the items of control information. In a mannercorresponding to the transmission channel explained with reference toFIG. 10, this transmission channel 2 includes two transformers 221, 222,two modulators 211, 212 and two demodulators 231, 232. In this example,the control circuit 1 generates two information signals S11, S12 at twooutputs 121, 122, of which the first information signal contains theswitching information and the second information signal contains theswitching parameter information. Two information signals S11′, S12′ arecorrespondingly available at the output of the channel 2, theinformation signals being fed to two inputs 311, 312 of the drivercircuit 3.

The driver circuit 3 can be designed to directly implement the switchingparameter information In2 received via the transmission channel 2, thatis to say to readily implement the information received. This meansthat, depending on the switching parameter information In2, anyarbitrary changes in the switching parameters are possible fromswitching operation to switching operation. In a further embodiment, thedriver circuit 3 is configured not to permit any arbitrary changes inthe switching parameters from switching operation to switchingoperation, but rather to limit these changes. It is based on theconsideration that great changes from switching operation to switchingoperation in the switching parameters received by the driver circuit 3can be caused by errors during transmission. The driver circuit can bedesigned for example to limit a change in the drive current S3 fromswitching operation to switching operation to a predefined maximumvalue. If this maximum permissible change is ΔS3max, for example, and ifthis maximum permissible change is smaller than a difference between aminimum possible drive current S3min and a maximum possible drivecurrent S3max, then a plurality of switching operations are necessaryuntil the drive current S3 can rise to the maximum value S3maxproceeding from the minimum value S3min and vice versa.

FIGS. 14 and 15 illustrate block diagrams of embodiments of the controlcircuit 1 and the driver circuit 3. In the example, the control circuit1 has a signal processing circuit 13, to which the switching signal S isfed and which generates the at least one information signal Si from theswitching signal S. The switching parameter information In2 is stored ina memory 14, such as a register 14, for example, which is connected tothe signal processing circuit 13. The memory can be given fixedprogramming ready from the manufacturer. However, the memory content canalso be given fixed programming by a user, or in one embodiment alteredduring operation, which is illustrated by dashed lines in FIG. 14. Byusing the content of this memory there is the possibility in oneembodiment, of adaptively setting the switching speed over a pluralityof switching operations of the transistor M. Adaptive methods forsetting the switching speed of a transistor are known, in principle, andso further explanations in this respect can be dispensed with.

The control circuit 1 can include further memories 15, 16, in which isstored for example the time duration Tr starting from which theswitching information is intended to be transmitted anew for the firsttime, or in which is stored a period duration Trp with which theswitching information is intended to be periodically repeated. Thecontrol circuit 1 can be realized as a microcontroller, in oneembodiment.

Referring to FIG. 15, the driver circuit 3 has a signal processingcircuit 33, to which the at least one information signal S1′ is fed. Acontrol signal S33 is available at the output of the signal processingcircuit 33 and drives a current source arrangement 35, which providesthe control signal S3. In this case, the current control signal S33determines both the current direction and the amplitude of the currentS3 provided by the current source arrangement 35. The driver circuit 3can contain a memory 34, in which is stored information about thetransmission time Tc within which the items of control information aretransmitted. The signal processing circuit 33 can use this informationto determine, after reception of a first signal pulse from the controlcircuit 1, the end of the transmission duration of the items of controlinformation and to set the sign and amplitude of the drive signal S3depending on the end of the transmission duration.

With regard to the memories explained in connection with FIGS. 14 and 15it should additionally be mentioned that these memories can also berealized as memories whose memory content is predefined by externalcircuitry, e.g., with resistors. In this case, however, the memorycontent can only be altered by changing the circuitry.

FIG. 16 illustrates an embodiment of a current source arrangement 35 ofthe driver circuit 3. This current source arrangement 35 has a number ofcurrent sources 361, 362, 36n, 381, 382, 38n, a first group 361, 362,36n of which are connected in parallel with one another and between aterminal for a first supply potential and the output 32 and a secondgroup 381, 382, 38n of which are connected in parallel with one anotherand between a terminal for a second supply potential, in the embodimentthe source potential of the transistor M, and the output 32. Thesecurrent sources can be activated or deactivated individually by acontrol circuit 40, to which the current control signal S33 is fed. Foractivating or deactivating the individual current sources, in theembodiment illustrated, switches 371, 372, 37n, 391, 392, 39n areprovided, one of which respectively is connected in series with one ofthe current sources and which are driven by the control circuit 40. Thecurrent sources are activated or deactivated in a manner dependent onthe control signal S33 with the aim of setting the current direction ofthe drive current S3 and the amplitude thereof. One or more currentsources 361, 362, 36n of the first group are driven for driving thetransistor M in the on state and one or more current sources 381, 382,38n of the second group are driven for driving the transistor M in theoff-state. The currents supplied by the individual current sources caneach be identical, but they can also be different.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments illustrated and describedwithout departing from the scope of the present invention. Thisapplication is intended to cover any adaptations or variations of thespecific embodiments discussed herein. Therefore, it is intended thatthis invention be limited only by the claims and the equivalentsthereof.

What is claimed is:
 1. A method comprising: receiving, by a drivercircuit, from a control circuit, switching information and switchingparameter information associated with a transistor, the switchingparameter information including switching speed information, wherein theswitching information and the switching parameter information arereceived for each switching operation of the transistor and based on aswitching signal received by the control circuit; and generating, by thedriver circuit, based on the switching information and the switchingparameter information, a drive signal associated with the transistor,wherein the drive signal is generated at a voltage or current level thatis dependent on the switching speed information.
 2. The method of claim1, further comprising receiving, by the driver circuit, from the controlcircuit, the switching information anew at least once after a waitingtime has elapsed since last receiving the switching parameterinformation.
 3. The method of claim 1, wherein the drive signal isgenerated at a first voltage or current level after the driver circuitreceives the switching information and the switching parameterinformation at a first time, the method further comprising, responsiveto receiving the switching information at a second time after the firsttime, generating, by the driver circuit, the drive signal associatedwith the transistor at a second voltage or current level.
 4. The methodof claim 3, wherein the second voltage or current level corresponds tothe first voltage or current level.
 5. The method of claim 1, whereinthe switching information comprises binary code.
 6. The method of claim1, wherein the switching information comprises a positive pulse or anegative pulse.
 7. The method of claim 1, wherein the switchingparameter information comprises binary code.
 8. The method of claim 1,wherein the switching parameter information comprises a positive pulseor a negative pulse.
 9. The method of claim 1, wherein the switchinginformation is received anew at least once during each switchingoperation of the transistor after a waiting time has elapsed sincereceiving the switching parameter information.
 10. The method of claim1, wherein the switching parameter information comprises at least oneof: signal level information indicating a maximum voltage or currentlevel of the drive signal, or delay information that defines a time todelay after receiving the switching information before generating thedrive signal.
 11. The method of claim 1, wherein the voltage or currentlevel of the drive signal defines a speed at which the transistorchanges switching states.
 12. The method of claim 1, wherein acombination of the voltage or current level of the drive signal and theswitching speed information define a switching edge of a load currentprovided by the transistor.
 13. A method comprising: receiving, by adriver circuit, from a control circuit, first switching information andswitching parameter information associated with a transistor, theswitching parameter information including switching speed information,wherein the switching information and the switching parameterinformation are based on a switching signal received by the controlcircuit; generating, by the driver circuit, based on the first switchinginformation and the switching parameter information, a drive signalassociated with the transistor, wherein the drive signal is generated ata voltage or current level that is dependent on the switching speedinformation; and receiving, by the driver circuit, from the controlcircuit, second switching information associated with the transistorafter a waiting time has elapsed since receiving the first switchinginformation.
 14. The method of claim 13, wherein the drive signal isgenerated at a first voltage or current level based on the firstswitching information, the method further comprising generating, by thedriver circuit, based on the second switching information and theswitching parameter information, the drive signal being at a secondvoltage or current level that is dependent on the switching speedinformation.
 15. The method of claim 14, wherein the second voltage orcurrent level corresponds to the first voltage or current level.
 16. Themethod of claim 13, wherein the switching parameter informationcomprises at least one of: signal level information indicating a maximumvoltage or current level of the drive signal, or delay information whichdefines a delay after receiving the first switching information or thesecond switching information before generating the drive signal.
 17. Themethod of claim 13, wherein the switching speed information indicates arate at which the transistor is to transition from an off-state to anon-state or from the on-state to the off-state.
 18. The method of claim13, wherein the switching speed information indicates a speed at whichthe transistor is to change switching states.
 19. A method comprising:receiving, by a driver circuit, from a control circuit, first switchinginformation and switching parameter information associated with atransistor, the switching parameter information including switchingspeed information, wherein the switching information and the switchingparameter information are based on a switching signal received by thecontrol circuit; generating, by the driver circuit, based on the firstswitching information and the switching parameter information, a firstdrive signal associated with the transistor, wherein the first drivesignal is generated at a voltage or current level that is dependent onthe switching speed information; and after a waiting time sincereceiving the first switching information and prior to receiving secondswitching information, generating, by the driver circuit, a second drivesignal associated with the transistor that drives the transistor to anoff-state of the transistor.
 20. The method of claim 19, wherein theswitching speed information indicates a an amount of time between whenthe transistor is to transition from a switch-off operation to aswitch-on operation or to transition from the switch-on operation to theswitch-off operation.